<template>
  <ul class="mo-paging">
    <!-- prev -->
    <!-- <li
      :class="['paging-item', 'paging-item--prev', {'paging-item--disabled' : index === 1}]"
      @click="prev"
    >prev</li>-->

    <!-- first -->
    <!-- <li
      :class="['paging-item', 'paging-item--first', {'paging-item--disabled' : index === 1}]"
      @click="first"
    >first</li>-->

    <li :class="['paging-item', 'paging-item--more']" v-if="showPrevMore">...</li>

    <li
      :class="['paging-item', {'paging-item--current' : index === pager}]"
      v-for="pager in pagers"
      :key="pager"
      @click="go(pager)"
    >{{ pager }}</li>

    <li :class="['paging-item', 'paging-item--more']" v-if="showNextMore">...</li>

    <!-- last -->
    <!-- <li
      :class="['paging-item', 'paging-item--last', {'paging-item--disabled' : index === pages}]"
      @click="last"
    >last</li>-->

    <!-- next -->
    <!-- <li
      :class="['paging-item', 'paging-item--next', {'paging-item--disabled' : index === pages}]"
      @click="next"
    >next</li>-->
  </ul>
</template>
<script>
export default {
  name: "MoPaging",
  //通过props来接受从父组件传递过来的值
  props: {
    //页面中的可见页码，其他的以...替代, 必须是奇数
    perPages: {
      type: Number,
      default: 5,
    },

    //当前页码
    pageIndex: {
      type: Number,
      default: 1,
    },

    //每页显示条数
    pageSize: {
      type: Number,
      default: 10,
    },

    //总记录数
    total: {
      type: Number,
      default: 1,
    },
  },
  methods: {
    prev() {
      if (this.index > 1) {
        this.go(this.index - 1);
      }
    },
    next() {
      if (this.index < this.pages) {
        this.go(this.index + 1);
      }
    },
    first() {
      if (this.index !== 1) {
        this.go(1);
      }
    },
    last() {
      if (this.index != this.pages) {
        this.go(this.pages);
      }
    },
    go(page) {
      if (this.index !== page) {
        this.index = page;
        //父组件通过change方法来接受当前的页码
        this.$emit("change", this.index);
      }
    },
  },
  computed: {
    //计算总页码
    pages() {
      return Math.ceil(this.size / this.limit);
    },

    //计算页码，当count等变化时自动计算
    pagers() {
      const array = [];
      const perPages = this.perPages;
      const pageCount = this.pages;
      let current = this.index;
      const _offset = (perPages - 1) / 2;

      const offset = {
        start: current - _offset,
        end: current + _offset,
      };

      //-1, 3
      if (offset.start < 1) {
        offset.end = offset.end + (1 - offset.start);
        offset.start = 1;
      }
      if (offset.end > pageCount) {
        offset.start = offset.start - (offset.end - pageCount);
        offset.end = pageCount;
      }
      if (offset.start < 1) offset.start = 1;

      this.showPrevMore = offset.start > 1;
      this.showNextMore = offset.end < pageCount;

      for (let i = offset.start; i <= offset.end; i++) {
        array.push(i);
      }

      return array;
    },
  },
  data() {
    return {
      index: this.pageIndex, //当前页码
      limit: this.pageSize, //每页显示条数
      size: this.total || 1, //总记录数
      showPrevMore: false,
      showNextMore: false,
    };
  },
  watch: {
    pageIndex(val) {
      this.index = val || 1;
    },
    pageSize(val) {
      this.limit = val || 10;
    },
    total(val) {
      this.size = val || 1;
    },
  },
};
</script>
<style  >
.mo-paging {
  display: inline-block;
  padding: 0;
  margin: 1rem 0;
  font-size: 0;
  list-style: none;
  user-select: none;
}

.mo-paging > .paging-item {
  position: relative;
  text-decoration: none;
  margin-left: -1px;
  cursor: pointer;
  display: inline-block;
  width: 40px;
  height: 40px;
  line-height: 40px;
  text-align: center;
  border-radius: 100%;
  border: 1px solid #d1d1d1;
  color: #cdcdcd;
  font-size: 16px;
  box-sizing: border-box;
  vertical-align: top;
  margin-right: 20px;
}

.mo-paging > .paging-item:first-child {
  margin-left: 0;
}

.mo-paging > .paging-item:hover {
  color: #b92b24;
  border-color: #b92b24;
}

.mo-paging > .paging-item.paging-item--disabled,
.mo-paging > .paging-item.paging-item--more {
  background-color: #fff;
  color: #505050;
}

.mo-paging > .paging-item.paging-item--disabled {
  cursor: not-allowed;
  opacity: 0.75;
}

.mo-paging > .paging-item.paging-item--more,
.mo-paging > .paging-item.paging-item--current {
  cursor: default;
}

.mo-paging > .paging-item.paging-item--current {
  position: relative;
  z-index: 1;
  color: #b92b24;
  border-color: #b92b24;
}
</style>
